What a BUMMER! Are you the original owner? If so, I'd be *****ing like hell to Alumaweld. That's an issue several boat manufactures had in the 70's and 80's and some of them "made it right" with the original owners. Foam shouldn't "wear out"! I've used gasoline to melt styro. out of "beauty or decorative" areas in concrete pours. It worked great, but you're talking about alot of by-product. Maybe a fillet knife and a shop vac too! Good luck and let us know what happens.